1. Field of Invention
The present invention relates to a substrate processing process. More particularly, the present invention relates to an apparatus and a method for spreading a processing liquid on the substrate.
2. Description of Related Art
Lithography is essential in the semiconductor process. Generally, the lithography process comprises the following steps: spreading a photoresist layer, exposing the photoresist layer to light, and developing the photoresist layer with a developer solution. For example, the photoresist layer of positive resists is exposed with UV light wherever the underlying material is to be removed. In these resists, exposure to the UV light changes the chemical structure of the resist so that it becomes more soluble in the developer. The exposed resist is reacted with the developer solution then washed away, leaving windows of the bare underlying material. On the other hand, negative photoresist behave in just the opposite manner. It is a material that becomes polymerized and insoluble when exposed to UV light. Therefore, the negative resist remains on the surface wherever it is exposed, and the developer solution removes only the unexposed portions. The pattern of the mask is transferred by these steps to the photoresist layer covering on the substrate.
The lithography process for manufacturing flat display panels is achieved by similar methods. After spreading photoresist on a substrate, a required pattern is defined by exposure, and a development process is then carried out. The development is preceded in a substrate development apparatus. FIG. 1A illustrates a schematic view of a conventional development apparatus. A substrate 110 is fixed on a substrate support unit 106. The substrate support unit 106 is positioned below the substrate 110, and holds the substrate 110 by vacuum or mechanical means.
A nozzle unit 104 is located above the surface of the substrate 110 for spreading developer solution on the substrate 110 to develop the photoresist. The conventional nozzle unit 104 has an injection port 112 and an exhaust port 114. A developer solution supply unit 102 provides the developer solution to the nozzle unit 104 circularly by the injection port 112 and the exhaust port 114.
FIG. 1B illustrates a process for of the substrate development apparatus in FIG. 1A. The developer solution supply unit 102 comprises a tank 132, a pump 134 and a temperature control device 136. After being pressurized by the pump 134 and the temperature thereof being adjusted by the temperature control device 136, the developer solution stored in the tank 132 is supplied to the nozzle unit 104 through the injection port 112.
As illustrated in FIG. 1B, when the developer solution is not needed, a valve 124 is opened such that the developer solution supplied to the nozzle unit 104 is circulated back to the developer solution supplying unit 102 through the exhaust port 114. In other words, the development apparatus is a circulating system at this time, and the developer solution is thus circulated inside to maintain its temperature. When the developer solution is to be spread, valve 124 is closed, and the developer solution supplied to the nozzle unit 104 is thus spread on the substrate 110 through the nozzle of the nozzle unit 104.
However, the length of the nozzle unit 104 becomes greater because the size of the substrate used for manufacturing display becomes larger, and the nozzle unit 104 has only one injection port 112, which is positioned on one side of the nozzle unit 104. When the developer solution is spread on the substrate 110 by the nozzle unit 104, a wave crest of the developer solution is easily generated on the substrate 110 because the pressures applied on the developer solution inside the two ends of the nozzle unit 104 are unbalanced.
FIG. 1C illustrate a schematic view of a conventional nozzle unit and a wave crest of the developer solution generated by the convention nozzle unit, and FIG. 1D illustrates a schematic view of spreading the developer solution on the substrate by the conventional nozzle unit. The following descriptions are made with reference to FIG. 1C and FIG. 1D.
As mentioned above, when the developer solution is spread, the developer solution is pressurized and supplied to the nozzle unit 104 through the injection port 112, which is positioned on one side of the nozzle unit 104. The pressure of the developer solution inside the nozzle unit 104 is decreased corresponding to the distance away from the injection port 112. In order words, the pressure of the developer solution near the injection port 112 is greater than the pressure of the developer solution distant from the injection port 112 (such as the pressure of the developer solution near the exhaust port 114). Moreover, the developer solution with the greater pressure passes through the nozzle of the nozzle unit 104 more easily. When the developer solution is spread by the conventional nozzle unit 104, a wave crest 142 of the developer solution is easily generated on the substrate 110 near the injection port 112.
For instance, the offset of the wave crest 142 of the developer solution generated by a nozzle unit 104 of which the length is 650 mm is about 50 to 100 mm. The offset of the wave crest causes suboptimal development such that the line width of the photoresist pattern is not uniform, and further affects the yield of products. More particularly, this suboptimal development especially affects the manufacturing of large-sized flat display panels.